In Big Bend - Chisos Basin - the campground hosts were issued air horns. The local bear (called Bart Simpson because of attitude issues) totally ignored sounds and any of the usual bear tricks. Even when I chased him with the campground truck - he just stepped of the road and gave me the finger.
What did work was tossing small branches and gravel. He ran for the nearest tree and prepared to climb it. Just to be clear - we were throwing small items so as to not hurt the bear. But my guess is that from the bear's perspective having things thrown is absolutely foreign; totally outside his experience.
Should this not work for you - have a plan "B".